Motion picture sound projector



Feb. 8, 1966 G. KAESS ETAL 3,233,958

MOTION PICTURE SOUND PROJECTOR Filed Oct. 24, 1962 Rrzokc LIVEL mun-nVOLUME L l r 27 1 7 7 l 4/ 3 4 M4;

Feb. 8, 1966 v G. KAESS ETAL 3,233,958

MOTION PICTURE SOUND PROJECTOR Filed Oct. 24, 1962 7 Sheets-Sheet 2Feb., 8, 1966 G. KAESS ETAL 3,233,958

MOTION PICTURE SOUND PROJECTOR Filed Oct. 24, 1962 7 Sheets-Sheet 3 Feb.8, 1966 G. KAESS ETAL 3,233,958

MOTION PICTURE SOUND PROJECTOR Filed Oct. 24. 1962 7 Sheets-Sheet 4 4 ifM I Feb. 8, 1966 s. KAEss ETAL 3,233,958

MOTION PICTURE SOUND PROJECTOR Filed Oct. 24, 1962 7 Sheets-Sheet 5 Feb.8, 1966 G. KAESS ETA]- MOTION PICTURE SOUND PROJECTOR Filed 001;. 24,1962 '7 Sheets-Sheet 6 Feb. 8, 1966 G. ss ETAL 3,233,958

MOTION PICTURE SOUND PROJECTOR Filed Oct. 24; 1962 7 Sheets-Sheet vezw/vpMf) I of; (46) United States Patent 3,233,958 MOTION PICTURE SOUNDPROJECTOR Gary Kaess, Boston, and Robert G. Palmer, Quincy, Mass.,assignors to Keystone Camera Company, Inc., Boston, Mass, a corporationof Massachusetts Filed Oct. 24, 1962, Ser. No. 232,712 12 Claims. (Cl.352-) This invention relates to motion picture projectors and moreparticularly to projector apparatus of the sound type.

Motion picture sound projector apparatus must be carefully engineered sothat the reproduced sound is properly synchronized with the projectedpicture images. This requirement dictates a precise spacing between thelocation of the image aperture of the projector and the sound head whichhas been standardized in the industry. Additional complexity isintroduced, however, due to the fact that the film must be stepped pastthe image aperture in an intermittent manner while for proper soundreproduction it is essential that the sound stripe on the film move pastthe sound head at a constant speed. It is necessary to isolate these twodistinct film movements from one another and for that purpose a numberof relatively complex filtering or isolation'arrangements have beendevised and utilized. While such filtering arrangements providesatisfactory isolation, they involve intricate film paths which makethreading of film through the projection apparatus difficult. Such filmpaths present particular problems in self-threading projector apparatusin which the film is. threaded through the projector by a single drivesprocket. Particularly in projectors of the type operated by thenon-professional there is demand for simple, trouble-free, easilyoperated apparatus of this type which is relatively inexpensive in cost.

Accordingly, it is an object of this invention to provide a novel andimproved. motion picture projector of the sound type which facilitatesself-threading.

In the recording of sound on motion picture film a sound stripe ofmagnetic material is often employed, which sound stripe is magnetized inaccordance with the sound that is to be recorded, This sound stripe ismoved past a sensing head at uniform speed and the recorded fluxpatterns are sensed by the pole piece and converted to electricalsignals which are in turn converted to audible signals in the form ofthe desired sounds. In order that the sound be properly reproduced thepole piece of the sensing head must be accurately aligned relative tothe sound stripe so that the desired signal coupling be achieved.Suitable sound head design for use with film of the eightmillimeter sizemust satisfy the available space requirements as well as beingcompatible with the image reproduction apparatus of the projector.

Accordingly, it is a further object of this invention to provide a noveland improved sound head structure for sensing magnetic flux patternsrecorded on a stripe of magnetic material.

A further object of the invention is to provide a novel and improvedsound head structure which facilitates the positioning of the sound headin optimum relation to the film sound track in a motion pictureprojector.

Another object of the invention is to provide a novel and improvedmotion picture sound projector in which the film sensing facilities forsound reproduction are inexpensive to manufacture while capable ofproducing sound of high quality.

Another object of this invention is to provide a novel and improvedmotion picture sound projector of the eightmillimeter size.

Still another object of the invention is to provide an improved motionpicture sound projector in which the sound head and a film drivesprocket are mounted coaxially with one another.

Still another object of the invention is to provide a novel and improvedmotion picture sound projector which employs a simplified film pathwhich facilitates self-threadmg operations.

Still another object of the invention is to provide a motion pictureprojector having improved film guide structures which facilitate thethreading of film.

A further object of the invention is to provide in a motion pictureprojector a novel and improved projector control mechanism responsive tothe movement of the film therepast.

A further object of the invention is to provide in a motion picturesound projector a novel sound head support structure which enables thesound head to be adjusted in a plurality of dimensions for accuratealignment with the sound drum and film supported thereby.

Other objects, features and advantages of the invention will be seen asthe following description of a preferred embodiment thereof progresses,in conjunction with the drawings, in which:

FIG. 1 is a side elevational view of an eight-millimeter soundprojection apparatus constructed in accordance with the invention;

FIG. 2 is a top view of the sound projector apparatus of FIG. 1; 7

FIG. 3 is a view taken from the rear of the sound projector shown inFIG. 1 showing details of the drive mechanism and control linkagesemployed therein;

FIG. 4 is a sectional view through the projector case taken along theline 4-4 of FIG. 3 showing further details of the drive and controlmechanisms;

FIG. 5 is a sectional view along the line 5-5 of 'FIG. 4 showing detailsof the clutch mechanism employed for driving the supply reel;

FIG. 6 is a sectional view taken along the line 66 of FIG. 4 showingdetails of the rewind drive mechanism;

FIG. 7 is a top plan view of the drive mechanism, speed control linkageand interlock employed in the projector apparatus;

FIG. 8 is a sectional view of the drive sprocket and sound head showingthe relationship of the film to those elements; 5

FIG. 9 is a sectional view of details of the sound head supportmechanism and associated structure adjacent to the sound drum;

FIG. 10 is a plan view of the sound drum and drive sprocket structurewith the sound head mount removed;

FIG. 11 is a sectional view along the line 11-11 of FIG. 9 showingadditional details of the sound drum and sound head mounting;

FIG. 12 is a top plan view of the sound head support structure;

FIG. 13 is a sectional view of the sound head structure taken along theline 13-13 of FIG. 12;

FIG. 14 is a side elevational view of the sound head and supportstructure;

FIG. 15 is a sectional view taken along the line'15-15 of FIG. 12 of thesound head looking in the opposite direction from that of FIG. 14;

FIG. 16 is a schematic diagram of the electrical circuitry employed inthe projector apparatus; and

FIG. 17 is a diagrammatic layout indicating the circuit connectionsresulting from the several possible positions of switch 47.

As shown in FIGS. 1 and 2, the sound projector has a casing 10 on whichis mounted a suitablesupport arm 12 on which is positioned a supply reel14 and at the upper rear corner of the casing front wall, a takeup reel16. Film 18, indicated by the dashed line, is fed past a first drivesprocket as guided by a fixed guide '22 and then via a movable guide 24to the projection aperture area disposed between the projection lamp 26and a lens unit 28. After passing the projection aperture, the filmenters a channel provided by a fixed guide 29 and a second movable guide30 and is fed rearwardly to a second drive sprocket 32 at which positionthere is also provided a sound drum that isrnouuted coaxially therewith.Disposed above the sound drum is a sound head structure generallyindicated at 34. 'At the discharge end of the sound drum sprocket thereis a third movable guide 36 which is pivoted about point 38 andcooperates with a fixed guide 39 to provide a guiding path for the filmto the takeup reel 16.

Several controls are mounted onthe lower part of the projector case inthe panel 40. These controls include a set of six push buttons 41-46which control opperations as follows:

Push button 41-Forward Push button 42-Still Push button 43-Revetse Pushbutton 44Thread Push button 45-Rewind Push button 46-Off Buttons 41, 43,44, 45 and 46 operate electrical contacts within switch assembly 47(FIG. 4.). Button 41 also operates a shifting interlock and button 45also operates a rewind linkage. Button 42 operates the still pictureclutch (a purely mechanical linkage). Further control is provided byknob 48 which has an off position and also control-s the sound volume;and knob 50 which controls the recording or playback operation of thesound system. Meter 52 indicates the record level, and directly belowthat meter is a speed selector lever 54.

Lever arm 55 controls the position of the sound head 34, the guide 36and the two rollers 56, 57 disposed adjacent sprocket 32.

A general understanding of the drive mechanism may be had with referenceto'FIG. 3. Inthe projector case there is mounted a motor 60 (on the:output shaft of which is mounted a two-step pulley) having diameters62, 64. A flexible belt-66is trained over the two-step pulley and overpulley 68 mounted on shaft 70. On one end of the shaft (the left end asviewed in FIG. 3) is a toothed pulley driving atiming belt 72 and on theopposite end of shaft there is mounted a worm gear 74 which engages ahelical gear 76 mounted to drive the tubular shaft 78 and sprocket 32.

The timing belt 72 is coupled by a toothed pulley 80 to shutter shaft 82mounted in suitable bearings for driving the shutter and intermittentclaw and through idler84 to drive gear 86'to which shaft 88 is securedfor driving sprocket 20. Gear 86 is connected through a reverse drivegear 90 to a driving gear'92 which is coupled through a one way clutchand a slip clutch to drive shaft 93 and a gear train to rotate thesupply reel 14 in the reverse direction. Drive shaft 83 has two bearings94 pressed in it and rotateson'a-stud 95 (FIG. 5).

Also shown in FIG. 3 is a high speed rewind drive which'includes afriction-cone that is mounted on the shutter shaft and which may beengaged with a cooperating conical friction capstan 102. Oapstan 102drives pulley 104 "overwh-ich'a belt106 is trained for driving pulley108 (FIG. 4). This overdrive is used for rewind and includes a linkagethat is operated 'by'the rewindpush'button 45. 'As shown in FIG. 4 thereis provided a first link member 110 mounted 'pivotally at its center ona'support secured-tothe projector frame. One end of link 100 is coupledto push button 45 and the other end-of the link member 110 is pinned tolink 112 that carries a stud 114 which acts against a third link member116 that is mounted for pivoting movement about stud 118. At the upperend of link116'therc is provided a roll 120 as best seen in FIG. 6. Roll120 is movable horizontally between a point in engagement with pulley104 and a point in engagement With cone 102,. When the rewind pushbutton 45 is depressed the linkage is operated to move stud 114 upwardlyagainst the biasing effect of toggle spring 122 against the camrningsurface 124 topivot link 116 about its pin 118 and force the cone 102into engagement with the cone 100 on the shutter shaft 82. When thisoccurs pulley 108 is driven via belt 106 and pulley-104 and thisover-riding force is coupled directly to the output gear 126 that iscoupled via the gear train in the supply reel support arm 12 to thesupplyreel '14. The advantage of this linkage system is that it has notendency to-push button 45 upwards thus breaking the electrical circuitwhich was established in switch 47 when button 45 was depressed. Absenceof pressure on the button is due to the 'followingco'rb ditions: stud114, in the rewind position, is pressing against the straight portion127 of camming surface 124, and thus there is no component force in thedownward directionyand toggle spring 122, in the rewind position, haspassed its center, and tends to push'link 112'upwards. When-the offbutton 46 is depressed at "the end'of the rewind operation, slidersinside switch 47 operate'to interrupt the electrical circuit and at thesame time to push up button 45. These sliders are rather delicate duetothe nature ofthe switch and should not be subjected to heavy forces.The rewind linkage systern p'uts very little strain on the sliders sincestud 114 can easily slide down the straight portion 127, and helps link1.12 move downwards, thus helping to lift button 45, and move thesliders in the switch. When stud 114 is halfway down the camming surface124, link 12 8 limits any further pressurebetween stud 1'14 and surface124. This lets roller 1 20 move away from cone 102, disengaging therewind overdrive. Also pulley *108 is further from'the center plate thanpulley 104, and this misalignment of belt 1 06 tends to urge cone 102away from cone 100. V

This structure provides a-idrive through gear'9'2'in the reversedirection when push button 43 is depressed. However, when the "rewindbutton 45 is depressed the mechanical linkageis operated to drive thepulley "108 at amuch'hig'her speed thanthe gear 92-isbeingdrive'n andthis higher speed is coupled directly and positively to the'reel driveeven'thoug'h gear 92remains driven.

When button 43 is depressed'the projector operates in reverse, andsprocket 20 feeds film at a constant rate to reel 14. The efiectivediameter of reel 14 varies with the amount'of film already on the reel.Therefore, reel 14 must rotate at a variable speed. To allow thereel-14to turn slower as it-ge'ts'fuller, gear 92 is permitted toslip on sleeve130 by means of a slip clutch. The'sli'p clutch consists'of frictionWashers 1 31 and'132 which are keyed to sleeve 130, and spring'washer133and back-up washer 134, and adjusting nut 135, and locking nut136.Thetension of the clutch isf'adjusted by compressing spring Washer 133to the desired degree by turning nut 135. In rewind the reverse slipclutch is bypassed, thus providing positive (slip free) drive to reel14. Thus this system provides a slow-speed variable-slip-drive inreverse: and a fast positive drive in rewind, whichover-runsthe. slowerreverse drive.

A similar type of slip clutch (not shown) isemployed to drive the takeupreel '16 by means of a chain drive' from the shaft 188. A similar oneway clutch structure is employed there so that the drive is engaged onlyin the: forward direction and is not engaged either'atthe normal reversespeed or at the higher rewind speed.

An interlock control is indicated in FIGS. 3, 4-and 7. This interlockcontrol is controlled by the'forward push button 41 and includes a leversupported on'a rotatable bar 142. At the opposite end of the'bar thereis mounted an arm 144 which in a normal position blocks movement or" tab"14"5'onlink 146. That link 146-is a.

part of the linkage connected to the speed control knob 54. That speedcontrol knob is mounted on a lever 148, pivoted at point 150 and coupledto an intermediate link 152 that connects links 148 and 146.

When the forward push button is depressed, the lock arm 144 is moved outof lock position and clear of up standing tab 145 to permit the movementof the speed selector switch. Mounted on the opposite end on the link146 from tab 145 is a pair of parallel upstanding pins 154, 156 whichare positioned on either side of belt 66. Movement of the speed selectorknob 54 causes the pins to engage belt 66 and move the belt from thelarger diameter section 62 of the pulley to the smaller diameter section64 and back again. In this manner control of the speed betweentwenty-four frames per second for sound operation and eighteen framesper second for silent operation is operative only when the projector isoperating in the Forward mode. This prevents damage to the belt and/orstalling of the drive motor, if an attempt to shift was to be made toshift while the projector is in off, reverse or rewind condition.

Also shown in FIG. 3 is the guide control mechanism for positioning theself-threading guides 24 and and at the same time the sound headstructure 34. During a threading operation guide 24 is down or loweredin loop forming position for guiding film into the projection aperturearea to form the desired loop configuration and guide 30 is in a raisedposition as shown in FIG. 1 to provide a second loop and to guide theend of the film into engagement with the teeth of sprocket 32. At thistime the sound head 34 is also raised. When the completion of thethreading operation is sensed, a mechanism is actuated to raise guide24, lower guide 30 and lower the sound head into position for operation.This operation is accomplished by solenoid 160 (shown in FIG. 3) whichhas an actuating arm 162 secured to a link 164 pivoted at pin 166. Theforward end of the link 164 has a slot 168 through which pin 170protrudes,

which pin is secured to the loop forming guide 24.

Immediately adjacent the actuating arm of the solenoid are two dependingrods 172, 1'74. Rod 172 is secured to the lower film guide 30 which ispivotally secured to the projector casing by a pin at point 176. Thesecond rod 174 is secured to the support structure for the sound .head34.

sation for the intermittent movement of the film produced by the filmadvancing claw. The intermediate guide 30 forms a second loop as thefilm is guided rearwardly into engagement with the sound sprocket 32 andfed from that sprocket to the output guide 36. When the film enters theguide 36 a sensor located there detects the presence of the film and mayoperate electrical circuitry to tie-energize solenoid 160 releasing theguides '24 and 30 and lowering the sound head so that the pole piece ofthe sound head is in engagement with the sound track on the film. Alsothis sensor may be used to automatically turn off the room lights and toenergize the projection lamp 26 for display of the images on the film.It may also be employed to turn off the projector and turn on the roomlamp when the films end has run through the sound sprocket.

The sound sprocket 32 structure is shown in greater detail in FIG. 8. Asthere indicated, the sound sprocket and film support structure has achannel 180 with surfaces 182, 184 on either side thereof on which thefilm is guided without any contact of the emulsion portion 186therewith. A guide controlling the passage of the film during thethreading of the film in engagement with the sprocket teeth is providedby wire 190 which has a curvature corresponding to that of the sprocketstructure 32. This wire does not touch the film during normal operation.This drive sprocket structure is mounted on a tubular shaft 78 to whichis secured the driving gear 76 by means of set screw 192 or othersuitable means. Gear 76 is driven by the worm gear 74 that is mounted onthe jack shaft 70. Mounted coaxially with the tubular shaft is a flywheel shaft 194 which is spaced therefrom by bearings 196, 198 so thatthe two shafts rotate independently. On the interior end of the flywheel shaft 194 is mounted a fly wheel 200 of substantial mass and onthe exterior end of shaft 194 is secured a sound drum structure 202which has a depressed surface 204 on which the sound stripe portion 206of the film is supported, the surface 204 being aligned with the filmsupport surfaces 182, 184 of the sprocket. Sound drum surface 204, whichhas a slightly greater radius than the sprocket film guide surfaces 182and 184, thus is free to rotate independently of the sprocket structureand its motion is principally controlled by the fly wheel 200.

The sound drum surface 204 is smoothly polished and the sound track 206of the film is maintained in frictional engagement with that surface bythe pressure of the pole piece 208 of the sound head structure 34 andpressure roller 56. The compliance characteristics of the film materialeffects decoupling of minor variations in the speed of the film producedfor example by changes in the spacing of the sprocket holes due to theshrinkage, aging of the film, etc. This film compliance is sufiicient sothat with the sound track portion thereof being directly coupled to themass of the fly wheel its instantaneous piece 208 of therecord-playback-head 210 is an erase head 212. The erase head 212 ispivotally mounted on the support structure 34 for adjustment toward andaway from the sound drum. It is spring-loaded against the drum and hasadjustments for tangency and azimuth. A first pressure roller 56 isbiased against the forward side of the film sprocket surface and asecond pressure roller 57 is biased against its rear surface. Each ofthese rollers is pivotally mounted on brackets 214 (FIG. 10) which aremounted for pivoting movement in clevis arrangements 216 supported onthe wall of the projector casing. Pressure roller 56 has an edge surface218 that is aligned with and normally biased into engagement with thesound drum surface 204 while pressure roller 57 has a similar surface220. Stop screw 222 (FIG. 10) is adjusted so that there is a gap ofabout .010" between roller surface 220 and drum surface 204. The guidewire 190, acting on the opposite edge of the film, tends to hold thefilm in contact with the sprocket drum surface 184 during the threadingoperation only. During projection the film 18 is under tension and ithugs surfaces 204, 182 and 184, thus leaving a clearance between it andthe guide wire.

Mounted to the rear of the sprocket structure is a cam 230, the bottomend of which is formed as a lever 232 that extends forwardly andprotrudes through the projector casing wall withknob 55 secured at theend hereof. This cam 230 is supported for rotative movement about theaxis of the sprocket by studs 234 and 236 that are received in slots 238and 240 respectivelyin the cam structure. The cam carries on its edgethree cam surfaces, at first surface 242 which acts against the bracket218 supporting roller 57, a second surface 244 which a cts against astud on the record-playback head support struc ture, and a third surface246 which acts against the 7 bracket 214 supporting pressure roller 56.In addition, the cam disc 230 carries a pin 248 which, when the cam discis fully rotated in the counterclockwise direction as viewed in FIG. 9,engages the film guide wire 1% and lifts it so that the film may beeasily released from the sprocket teeth.

'In the position shown'in FIGS. 9-11 the cam disc is in the soundposition with both pressure rollers acting to urge the film into contactwith the sound drum surface and the pole piece 2% of the record-playbackhead also being biased down by spring 25% into engagement with the filmon the sound drum surface. Movement of the cam disc in thecounterclockwise direction to a position where the arm 232 is directlybelow the axis of the disc (silent operation) positions the cam surface244 so that the pole piece 203 of the record-playback head and th erasehead 212 are lifted from engagement with the film so that the projectormay be operated in the silent mode. Full movement of the cam disc in thecounterclockwise direction brings the other-two cam surfaces 242, 245into engagement with the brackets and pin 2.4.8 acts against the wire199, lifting these structures away from the sound drum surface andpermitting access to the film that is engaged by the sprocket teeth.This movement also urges pressure roller 57 against the stud 252 whichis carried .by the movable portion 36 of the output film guide. As

indicated above, that film guide portion is pivoted at its upper end andthis movement opens the space between the fixed guidepor'tion 39 and themovable guide portion 36 so that access to the film in that area may behad. As guide ,36 pivots to open, the edge 254 of the slot through whichsensing wire 256 of switch 253 protrudes, pushes againstwire 256 andmoves it out of the slot, so that the film may be removed or inserted atwill.

Details of theconfiguration of the record-playback head mountingstructure is shown in FIGS. 12'15. That support structure 34 is mountedon a shaft 28% that extends outwardly from the wall of the projectorcasing '10. A collar portion 28-2 fits over the shaft 280 and a bushing284 and threaded stud 286 secure the support head casting on this shaft232. Spring 250 has one end engaged on pin 290 that is secured to thecasing wall and the other end acting above the stud 292 on the supportcastingso that the spring 256 acts to bias the head in a direction ofclockwise rotation (as viewed in FIG. 9) about the shaft 28%. On theopposite side of the casting there is a tab 294 which carries astud 296and a lock nut 298. This bottom of the-stud engages a tab 3%)!) thatforms a part of the projector casing wall and this mechanism providesanadjustable limit of the rotation of the support castingso that thepole piece 208 supported thereon may be accurately positioned parallelto the stripe 296 (FIG.

.8). This is known'as the bearing or facing adjustment.

For proper sound reproduction the sound head and particularly pole piece208 must be accurately adjusted relative to the sound track. This soundhead mounting permits the following adjustments in addition to thefacing adjustment: Tangency; azimuth; pressure. These adjustments permitthe pole pieces 208 to be precisely aligned relative to the sound stripeof the film. For proper operation the gap between the pole pieces shouldbe at a point exactly tangentto the curvature of the sound drum(tangency adjustment) or loss of signal will result. Further, the planeof the pole pieces'should be parallel to the sound stripe (azimuthadjustment) or there will be some loss of high frequency signals, andthe pole piece surface should be exactly parallel (in the planeperpendicular to thedirection of movement of the film) for proper soundsensing (facing adjustment). Also, the pressure of the pole piece on thefilm should be adjustable within a working range so that there will beadequate contact with the sound track while preventing the. polepiecefrom .contacting the sound drumphysically. These and other 8 adjustmentsare provided by the structure shown in FIGS. 12-15.

As indicated above, the sound head structure has a main support platewhich is pivotally mounted on shaft 280. The spring 250 which actsagainst studs 292 to bias the main support structure downwardly in aclockwise direction as viewed in FIG. 13 about the shaft 280 alsoprovides a force for biasing the structure outwardly. The distance ofthe sound head structure from the projec tor casing is adjusted by thethreaded bushing 284 which cooperates with shaft 286 and the lock screw286 which provides a lock when the proper position has been achieved.

Supported within this main support structure is a second support member31 which is mounted on two pivot screws 312, 314 that are aligned on anaxis at the center of the pole pieces so that this second plate 310 maybe pivoted about that axis to provide a tangencyadjustment. The pivotalposition of this intermediate plate 310 is controlled by a tangencyspring 316 which tends to pivot the plate 310 in a clockwise directionas viewed in FIG. 13. Counterbalancing spring 316 is the tangency adjustscrew 318 permitting adjustment and locking of 2 support plate 310relative to the axis defined by pivot screws 312, 314.

Secured to the plate Slit is a bracket member 320 which has a fiat uppersurface mated against the lower surface of the plate 310 and securedthereto by a stud 322 that has a threaded lower portion 324 and acentral bearing portion 326 so that the bracket member 320 may berotated relative to the plate 310. This stud 322 provides an azimuthpivot which is vertically aligned with the gap of pole piece 208. Alongthe pivot axis to the rear thereof is provided an azimuth lock screw 330which has a washer 332 under its head and is threaded into the bracketmember 320. This azimuth lock screw passes through an enlarged bore inthe plate 310 so that a degree of rotation about the azimuth pivot ispermitted. A hole in the main support immediately above the azimuth lockprovides access for tightening the azimuth lock screw 330 when thebracket structure is properly positioned so that the pole piece isexactly parallel to the sound stripe on the film.

Carried by the bracket member 320 is a sound head support structure 340in which the sound head 210 is secured by conventional means. Thissupport member has a flat upper surface and a rearwardly extending arm342 which is received between the arm members 344 of the bracket 320 andpivotally secured there be the conically pointed screws 3%, 34 8 so thatthe head structure is free to rotate about the pivot defined by thosetwo screws. This pivot axis defined by the screws is parallel to thetangent line between the sound drum and the pole piece. In addition,there is the head stop screw 350 and a pressure adjusting screw 360. Thehead stop screw 350 has a disc-like portion 352 at its lower end onwhich a lower surface of the support 340 rests as best seen in FIG. 13.This screw 350 is adjusted until there is a minimum gap (about 0.0005")between pole piece 203 and drum surface 204 (FIG. 8). The pressureadjusting screw 360 is secured in a threaded hole in bushing 364 carriedby the plate 310. A sleeve 366 in the lower portion of bushing 364 isbiased by the coaction of the stud 360 and spring 368 to provide apressure adjustment or release for the sound head.

It will be noted that while tangency spring 316 acts against the plate310 and the cooperating tangency adjust 9 368 and allow the head torise, thus alleviating the pressure at that point. Thus the sound headstructure permits adjustment of the record-playback head in the severalplanes in a compact, easily adjusted, and accurately alignablestructure.

With reference now to FIGS. 16 and 17, power is supplied to theprojector apparatus from a conventional 110 volt supply at standardfrequency through a plug connector 380. Supply line 382 has a connectionto terminal FS of the slide switch unit 47; a second connection to thecommon terminal of film sensor switch 258; and a third connection toterminal 383 of the light control switch 384. The second supply line 386has a first connection to terminal L of the slide switch 47 and throughcapacitor 388 to winding 389 of the drive motor 60; a second connectionto the coil of solenoid 160; a third connection to one terminal of aroom light circuit indicated generally at 390; and a fourth connectionto the primary winding 392 of transformer 394.

The transformer 394 is connected so that its secondary 396 (includingcenter tap 398) supplies a DC. power supply circuit 400 under thecontrol of switch 402 for energizing the sound amplifier circuitry. Theprimary winding 392 of the transformer has a tap 404 which provides an18 volt signal and a tap 406 which provides a 21 volt signal. These tapsare connected to terminals 405, 407 respectively of the light controlswitch 384. Additional terminals 408, 409 are connected to theprojection lamp 26.

The light control switch has a control member 410 having two sliderswhich are movable between a middle position in which the slider shortsthe two center terminals toward either end where connection is madebetween a center terminal and the end terminal. In the intermediateorcenter position a circuit is completed from line 382 through terminal383, the left hand shorting slider 411 and terminal 412 through the roomlight 390 to the line 386 so that the room light line is alwaysenergized when the switch is in that position. In either end positionthis room light circuit is interrupted. At one of the end positions (theupper as shown in FIG. 16) the projection lamp 26 is connected to thehigher voltage tap 406 through terminal 407, slider 413 and terminal 408and at the other end position the lamp 26 is connected to the lowervoltage tap 404 through terminal 405, slider 413 and terminal 409. Thispermits control of the lamp intensity to permit adjustment for slowmotion or still viewing as desired or to reduce the lamp intensity sothat longer effective life of the film may be obtained.

With reference again to the slider switch 47, one group of fourterminals (labeled L are connected to normally open contacts 420 of thefilm sensor switch 258. Two terminals (labeled F) in the same row areconnected to winding 422 of the motor, and the remaining two terminals(labeled R) are connected to the opposite winding 424 of the motor. Inthe second row of slide switch terminals a group of three terminals(labeled W) are connected to winding 426 of the motor. In that same rowthere is a terminal labeled PL which is connected to the projection lamp26 and also to a terminal of transformer primary 392. Cooperating withthat terminal (which is connected to a normally opened contact (see FIG.17)) is a terminal (labeled RML) (which is connected to a normallyclosed contact) and is connected to the room light 390. Finally, theterminal labeled THD 1s connected to the solenoid coil 160.

This circuitry provides in the slide switch, connected as indicated inthe diagram of FIG. 17, control over the film drive operation of thesound projector. When the forward push button 41 is depressed, the fourcontacts (indicated by Xs in the horizontal line) are closed and theother five contacts (indicated by circles) remain open. With thecircuitry position shown in FIG. 16 when the forward push button isdepressed the motor windings are connected for operation in the forwarddirection; but no power is supplied to the motor to drive it in theforward direction since no connection is completed to line 382. Thatrequired connection exists however when the film sensor switch 258 isopera-ted by the presence of film past the sound head to complete thecircuit to contacts 420. This interlock prevents film threadingoperations when the forward push button is depressed. Rather, the threadpush button 44 must -be depressed which closes the six contacts asindicated in the diagram of FIG. 17. Circuits from line 382 arecompleted through terminals FS and THD to energize the solenoid placingthe movable loop formers in threading position, and raising the soundhead; through terminals FS and RML to maintain the room light circuitenergized; and through terminals FS and W to the motor in circuit foroperation in the forward direction. When the film has been threaded pastthe sound drum into the output guide the film sensor element 256actuates switch 258 to open the normally closed contacts and to closecontact 420 to complete a circuit from line 382 to the terminal L Thepresence of film in that position thus completes a circuit that bypassesthe contact P3 of the slide switch and in this condition the depressionof the forward push button will operate the film drive of the projector.

After threading is completed, the depression of the forward push buttonautomatically releases the circuits completed by the depressed threadpush button and completes the forward circuits. By this operation thecontrol solenoid 160 is de-energized retracting the loop forming membersto their inoperative position out of engagement with the film andlowering the sound head structure into contact with the sound stripe ofthe film. Also the operation switches from the room light circuit to theprojection lamp circuit (from terminal RML to terminal PL). (In theabsence of film it will be noted that the room light will remainenergized at all times.) When the film is present the projection lampcircuit is completed (for forward operation) and that lamp may be turnedon by placing the switch element 410 of the switch 384 in either of theend positions, which operation de-energizes the room lamp and turns onthe projection lamp. When the end of the film passes the sensor 258 theroom light 390 again is automatically energized. Also should theprojector lamp 26 be extinguished by the operation of'the lamp switch384 at any time the room light also will be energized-at the same time.

Depression of the still push button 42 does no release any of thecircuits completed by the previously depressed push button, but ratheronly operates a clutch to disengage the film drive circuitry from themotor 60. Should the reverse push but-ton 43 be depressed circuits willbe completed (without the film sensor interlock) to display film imageswhile the film is being driven in the reverse direction. (The interlockis not necessary since film cannot be self-threaded when the drivesprockets are operating in the reverse direction.) When the rewind pushbutton 45 is depressed the previously completed circuits are releasedand the indicated circuits are completed energizing the room lightindependently of the presence of film or the position of the projectorlamp switch, de-energizing the projector circuit and operating thecamera motor in the reverse direction (with the high speed drive beingoperated by the mechanical linkage). Depression of the oif push button46 completes a circuit to room light only.

It will be understood of course that additional circuits may becontrolled by the film sensor. For example, solenoid 160 could beautomatically de-energized when presence of film was sensed, and/or theprojector lamp circuit could be automatically completed. Such a circuitenables an automatic transfer from thread to forward operation inresponse to film position. In one possible circuit arrangement contact420 would be connected directly to the projector lamp 26 and theterminal of transformer primary 392 and a normally closed fihn sensorcontact would be employed in series with solenoid 169. The projectorlamp and room light terminals in the slide switch could also beeliminated with primary light control being provided by switch 284.

Thus the invention provides improved sound projector .apparatusparticularly adapted for self-threading type ,of operation for handlingeight-millimeter film. The invention provides a simplified film path andsound structure configuration in a compact, economical and easilyadjustable unit. An interlock is provided which a-ctuates electricalcircuits when the completion of the film threading operation is sensedto enable normal projector operation, which interlock also preventsimproper positioning .of projector components in a threading operationwhich might result in damage to the film. The sound head structure ismounted in a manner which permits ready positioning of the sound headbetween a sound position and a silent position, and a third'position inwhich all components, including thread guides, are released so that thefilm may be easily removed from the projector; In addition to beingcompact in design, suitable for use in conjunction with eight-millimetersize film, the sound head structure includes provision for tangency,facing and pressure adjustments so that the proper alignment of thesound head pole piece relative to the film sound stripe may be easilymade and accurately made,

7 While a preferred embodiment of the invention has been shown anddescribed, various modifications thereof will. be obvious to thoseskilled in the art and therefore it is not intended that the inventionbe limited to the disclosed embodiment or to details thereof anddepartures may be made therefrom within the spiritand scope of theinvention as defined in the claims.-

We claim! 1. A motion picture sound projector for use with motlonpicture film having a sound stripe portion extending along onesidethereof comprising a first drive sprocket,

afixed. film guide adjacent said first drive sprocket defining a filmpassage entrance to said first drive sprocket,

a movable loop forming member having a concave downwardly film guidingportion disposed rearwardly of said first drive sprocket,

said loop forming member being movable between a lower threadingposition and an upper running position,

a film gate,

a projector lamp disposed behind said film gate,

an aperture insaid film gate for passing light from said projector lampthrough said film,

a second movable loop forming member having a concave upwardly filmguiding portion,

said, second loop forming member being movable between 21 threadingposition and a lower running posi- Lion and extending from the endof'said film gate in a generally rearward direction,

a second drive sprocket adjacent the terminal portion of said secondloop forming member,

a sound drum mounted coaxiaily with said second. drive sprocket forrotation independently thereof,

said sounddrum including a circumferential surface for supporting thesound stripe portion of the film only,

an output film guide structure disposed rearwardiy of said second drivesprocket to receive film therefrom for guiding to the takeup reel,

a sound head disposed immediately adjacent said sound drum including apole piece adapted to be positioned in, engagement with the sound stripeof film supported; on said sound drum,

means to lift said sound head and to place said first and second loopforming members in threading position so that film placed in engagementwith the teeth of said first drive sprocket is automatically fed by saidfirst drive sprocket through the threading path andacross said seconddrive spro t and sound drum solely as urged by said drive sprockets in aselfthreading operation, film sensor means disposed in said output filmguide structure, and means responsive to the sensing of film in saidoutput film guide structure by said film sensor means ,to lower saidsound head into engagement with the sound. stripe portion on said sounddrum.

2. The motion picture projector as claimed in claim 1 and furtherincluding means responsive to said film sensor means to enable normaldrive operation of said pro.- jector.

3. The motion picture projector as claimed in claim 1 and furtherincluding means for biasing said film into engagement with said sounddrum and means for simultaneously lifting said sound head and said filmbiasing means to enable removal of film from said second sprocket.

4. The motion picture projector as claimed in claim 1 and furtherincluding means responsive to said film sensor means to enable theenergization of said projector lamp.

5. A motion picture sound projector for use with motion picture filmhaving a sound stripe portion extending along one side thereof,comprising a drive sprocket having a film support surface and aplurality of teeth for en.- gaging and driving motion picture film,

projector drive means for rotating said drive sprocket,

a first upstanding flange adjacent said film support surface on saiddrive sprocket for engaging and guiding one edge of said film,

a sound drum mounted coaxially with said drive sprocket for rotationindependently thereof,

said sound drum including a circumferential surface for supporting thesound stripe portion of the film only and an upstanding flange spacedfrom said sprocket flange for engaging the opposite edge of said film,

means for adjusting the spacing between said flanges,

means to bias said film into engagement with said sound drum surface,

a fiy wheel secured to said sound drum for imparting rotational inertiato said sound drum,

a sound head disposed immediately adjacent said sound drum including apole piece adapted to be positioned in engagement with the sound stripeof film, supported on said sound drum,

and means to lift said sound head and said filrn biasing means incoordinated manner to enable removal of film from said drive sprocket.

6. The motion picture projector as claimed in claim 5 wherein saidlifting means includes a cam member mounted for rotation about the sameaxis as said drive sprocket and said sound drum.

7. The motion picture projector as claimed in claim 5 and furtherincluding a support structure for positioning said sound head inaccurate alignment relative to said sound stripe comprising a firstmember securing said sound head with said pole piece disposed generallyparallel to the direction of movement of said sound stripe past saidpole piece,

a bracket member secured to said first member and mounted so that saidpole piece is rotatable about a first axis perpendicular to thedirection of movement of said sound stripe and passing through said polepiece,

a plate member supporting said bracket member,

said plate member being supported for pivoting movement about a secondaxis perpendicular to said first axis and parallel to the direction ofmovement of said sound track,

a main support structure,

and means securing said plate member to said main support structure forpivoting movement about said second axis.

8. The motion picture projector as claimed in claim 7 and furtherincluding resilient means secured to said plate member and acting tourge said sound head into engagement with said sound stripe andadjust-able stop mean-s acting to limit the movement of said sound headin response to the urging of said resilient means.

9. The motion picture projector as claimed in claim 6 wherein said soundhead is mounted for pivoting movement on the case of said projector andfurther including resilient means disposed between said sound head andsaid projector case acting to pivot said sound head into engagement withsaid sound stripe and adjustment means including an element secured tosaid case and an element carried by said sound head support structureacting with said resilient means to control the bearing position of saidpole piece relative to said sound stripe.

10. The motion picture projector as claimed in claim 6 and furtherincluding adjustable means for moving said sound head in a directionparallel to said drive sprocket axis for properly positioning said polepiece relative to said sound drum support surface.

11. A motion picture projector comprising a drive sprocket for engagingand advancing film and including a flange for engaging one side of thefilm,

a sound drum mounted coaxially with said drive sprocket for rotationindependently thereof,

said sound drum having a corresponding flange for engaging the oppositeside of the film and a circum ferential support surface adjacent saidsound drum flange on which the sound stripe portion of the film normallyrests.

means 'for adjusting the spacing between said drive sprocket flange andsaid sound drum flange to properly position the film with respect tosaid support surface,

a sound head disposed adjacent said sound drum surface having a polepiece adapted to engage the sound stripe portion of said film,

roller means disposed on either side of said sprocket for guiding filminto driving engagement with said sprocket and biasing said sound stripeinto engagement with said sound drum surface,

and cam means disposed adjacent said sound head and said roller meansfor moving said sound head and said roller means, said cam means havinga first position permitting said roller means to resiliently engage filmtrained over said sound drum surface and said sound head pole piece tobe in contact with said film for projector operation in the sound mode,

a second position in which said rollers and said sound head are movedclear of said sound drum and drive sprocket so that film may be removedtherefrom,

and an intermediate position between said first and second positionsWhere said sound head only is lifted from contact with said film forprojector operation in the silent mode.

12. The motion picture projector as claimed in claim 11 and furtherincluding film guide means comprising an elongated narrow curved elementnormally disposed adjacent to but spaced from said drive sprocket flangefor guiding film onto said drive sprocket,

and means carried by said cam means for moving said curved element awayfrom said drive sprocket as said cam means is moved from said firstposition to said second position.

References Cited by the Examiner UNITED STATES PATENTS 1,987,406 1/1935May 88-16.2 2,023,065 12/1935 Conrad et a1 352-29 2,127,143 8/1938 Ross88-16.2 2,912,519 11/1959 Simmons 179*100.2 2,943,860 7/1960 DArcy 274-4JULIA E. COINER, Primary Examiner.

WILLIAM MISIEK, Examiner.

1. A MOTION PICTURE SOUND PROJECTOR FOR USE WITH MOTION PICTURE FILMHAVING A SOUND STRIPE PORTION EXTENDING ALONG ONE SIDE THEREOFCOMPRISING A FIRST DRIVE SPROCKET, A FIXED FILM GUIDE ADJACENT SAIDFIRST DRIVE SPROCKET DEFINING A FILM PASSAGE ENTRANCE TO SAID FIRSTDRIVE SPROCKET, A MOVABLE LOOP FORMING MEMBER HAVING A CONCAVEDOWNWARDLY FILM GUIDING PORTION DISPOSED REARWARDLY OF SAID FIRST DRIVESPROCKET, SAID LOOP FORMING MEMBER BEING MOVABLE BETWEEN A LOWERTHREADING POSITION AND AN UPPER RUNNING POSITION, A FILM GATE, APROJECTOR LAMP DISPOSED BEHIND SAID FILM GATE, AN APERTURE IN SAID FILMGATE FOR PASSING LIGHT FROM SAID PROJECTOR LAMP THROUGH SAID FILM, ASECOND MOVABLE LOOP FORMING CHAMBER HAVING A CONCAVE UPWARDLY FILMGUIDING PORTION, SAID SECOND LOOP FORMING MEMBER BEING MOVABLE BETWEEN ATHREADING POSITION AND A LOWER RUNNING POSITION AND EXTENDING FROM THEEND OF SAID FILM GATE IN A GENERALLY REARWARD DIRECTION, A SECOND DRIVESPROCKET ADJACENT THER TERMINAL PORTION OF SAID SECOND LOOP FORMINGMEMBER, A SOUND DRUM MOUNTED COAXIALLY WITH SAID SECOND DRIVE SPROCKETFOR ROTATION INDEPENDENTLY THEREOF, SAID SOUND DRUM INCLUDING ACIRCUMFERENTIAL SURFACE FOR SUPPORTING THE SOUND STRIPE PORTION OF THEFILM ONLY, AN OUTPUT FILM GUIDE STRUCTURE DISPOSED REARWARDLY OF SAIDSECOND DRIVE SPROCKET TO RECEIVE FILM THEREFROM FOR GUIDING TO THETAKEUP REEL, A SOUND HEAD DISPOSED IMMEDIATELY ADJACENT SAID SOUND DRUMINCLUDING A POLE PIECE ADAPTED TO BE POSITIONED IN ENGAGEMENT WITH THESOUND STRIPE OF FILM SUPPORTED ON SAID SOUND DRUM, MEANS TO LIFT SAIDSOUND HEAD AND TO PLACE SAID FIRST AND SECOND LOOP FORMING MEMBERS INTHREADING POSITION SO THAT FILM PLACED IN ENGAGEMENT WITH THE TEETH OFSAID FIRST DRIVE SPROCKET IS AUTOMATICALLY FED BY SAID DRIVE SPROCKETTHROUGH THE THREADING PATH AND ACROSS SAID SECOND DRIVE SPROCKET ANDSOUND DRUM SOLELY AS URGED BY SAID DRIVE SPROCKETS IN A SELFTHREADINGOPERATION, FILM SENSOR MEANS DISPOSED IN SAID OUTPUT FILM GUIDESTRUCTURE, AND MEANS RESPONSIVE TO THE SENSING OF THE FILM IN SAIDOUTPUT FILM GUIDE STRUCTURE BY SAID FILM SENSOR MEANS TO LOWER SAIDSOUND HEAD INTO ENGAGEMENT WITH THE SOUND STRIPE PORTION OF SAID SOUNDDRUM.